inorganic chem

Atomic radius across a period

Across a period, nuclear charge increases, number of inner shell electrons remain the same and shielding effect remains relatively constant. Hence, nuclear attraction for valence electrons increases and atomic radius decreases

Atomic radius down a group

Down a group, nuclear charge increases and number of filled electronic shells increase. Hence, valence electrons are further away from nucleus and experience greater shielding effect which outweighs the increasing nuclear charge. hence, nuclear attraction for the valence electrons decrease and atomic radius increases

Cations vs corresponding atom

Nuclear charge remains the same for cations while nuclear attraction for the valence electrons in cations is stronger as the same number of protons are attracting fewer number of electrons, hence cations have smaller ionic radius

Anions vs corresponding atom

Nuclear charge remains same for anions while nuclear attraction for the valence electrons in anions is weaker as the same number of protons are attracting more number of electrons, hence anions have larger ionic radius

Across isoelectronic series, eg Na+ vs Mg2+

Nuclear charge across isoelectronic series increases while number of electrons remain the same. Nuclear attraction for the valence electrons increase as more protons are attracting same number of electrons. hence, ionic radius decreases

anions vs cations in same period

Anions have higher nuclear charge and one additional filled electronic shell than cations in the same period. Nuclear attraction for the valence electron in anions is weaker as the valence electrons are further away from the nucleus and have greater shielding effect which outweigh the higher nuclear charge in anions. Hence, anions have bigger ionic radius

First ionisation energy definition

First ionisation energy of an element is the energy required to remove one mole of most loosely held electrons from 1 mole of gaseous atoms of the element to form 1 mole of singly charged gaseous cations. (X(g)→X+(g) +e-)

IE down a group

Down a group, nuclear charge increases and number of filled electronic shells increase. Hence, valence electrons are further away from nucleus and experience greater shielding effect which outweighs the increasing nuclear charge. hence, nuclear attraction for the most loosely held electron decreases and less energy is required to remove the electron and first IE decreases

IE across a period

Across a period, nuclear charge increases, number of inner shell electrons remain the same and shielding effect remains relatively constant. Hence, nuclear attraction for the most loosely held electron is stronger and more energy is required to remove it hence first IE increases

Small dip in first IE between group 2 and group 13 elements, Eg Mg and Al

The most loosely held electron of Al is in the higher energy 3p subshell while that of Mg is in the 3s subshell. This outweighs the higher nuclear charge in Al. Hence nuclear attraction for the most loosely held electron of Al is weaker and less energy is required to remove this electron, resulting in lower first IE

Small dip in first IE between group 15 and group 16 elements, eg P and S

The most loosely held electron of S is in a doubly filled 3p orbital while that of P is in a singly filled 3p subshell. The most loosely held electron in S experiences inter electronic repulsion with its paired electron which outweighs the higher nuclear charge in S. Nuclear attraction for this electron in S is weaker and hence less energy is required remove this electron in S, resulting in lower first IE

Sharp drop in first IE between group 18 and group 1 element of next period, eg Ar and K

The most loosely held electron of K is removed from electronic shell n=4 while that of Ar is from n=3. The most loosely held electron is further away from the nucleus and experiences greater shielding effect. this outweighs the higher nuclear charge in K and the nuclear attraction for this electron is weaker. hence less energy is required to remove this electron and first IE of K is much lower